F-14 Questions Answered - Ask Away

[Tempest]

Slightly /forums/graemlins/32.gif

Quote:
note that airliners lose thrust at high speed,

Can you explain a little about this? I always thought jet engines would increase thrust at higher speeds due to the increased volume of air going through them.

 

[Astro14]

Originally Posted By: tom slick
What did the F-16N feel like compared to the F-14 and F-18?

The F-16N was a stunt plane...really...it was an older block F-16 airframe, with the latest model big engine, and was delivered without the gun installed, so it was much lighter than the F-16s that came with the big engine and it would out-perform everything in the air...

In an F-14A, it was losing proposition to fight that F-16N straight up...a good driver could capitalize on a mistake...in a 2v2 or a 4vX...a couple of quick kills, or a long-range pre-merge kill would give the Tomcat drivers a chance to gang up on the F-16s and win...but it was a hard, hard fight...

The F-14B/D had a better chance with the bigger engines, but the F-16N still had the advantage...

In the F-14 Training Squadron, (known in the Navy as FRS or RAG), we would take the Tomcats and students down to NAS Key West in the winter to take advantage of dedicated airspace and good weather to do air to air tactics training.

In Key West, I was lucky enough to fly in the F-16N a few times, once with a good friend (from my first fleet squadron, now we're neighbors...) and the jet is (or was) really impressive: easy to fly, great energy addition, great roll rate...we had fun, but I will tell you that 9G just plain hurts...I could take 7.5G all day long...but I had a serious set of G-measles from that flight and could feel the tingle/burn when we went for the high-G rate fight vs. a student in the F-14...

But to be honest, those F-16Ns were "rode hard and put away wet"...they saw nothing but short, intense flights at max G and max airspeed...not the average set of mission profiles that GD intended for the airplane and on which the fatigue models were predicated. The jets should have been good for a 6,000 hour life in normal use...and all of ours had major structural/fatigue issues (bulkhead cracks, etc.) when they got to about 1,000 hours...

This was in the mid 90s...declining budgets, etc...so the decision was made to retire the F-16N and use surplus F/A-18A models as adversary airplanes. The Hornet is a great airplane...and while it was brilliant in slow-speed handling/maneuvering, it couldn't quite match the incredible speed and energy addition of the F-16N...

 

[Astro14]

Originally Posted By: Tempest
Slightly /forums/graemlins/32.gif

note that airliners lose thrust at high speed,

Can you explain a little about this? I always thought jet engines would increase thrust at higher speeds due to the increased volume of air going through them.

Basic aero stuff...has to do with the mass of the airflow going through the engine. The high-bypass turbo fans cannot handle the increased volume of air...they do their best work at lower speed...the high-bypass gives better fuel specifics...but at high speed, there is a decrease in net thrust.

The intakes on jets like the F-15, SR-71, F-14 are all designed to handle supersonic flow and compress/decelerate the air as it enters (shockwaves form, and the inlets adjust dynamically to maintain the shock front and inlet air flow stability)...so airplanes with variable geometry inlets have a higher top speed as they manage the airflow...

More here: https://en.wikipedia.org/wiki/Turbofan

 

[Astro14]

Top Gun?

How accurate was this sequence? (Sort of? Not at all? 100% movies?)...

- iceman

Sequences like this were filmed for visual impact, not tactical accuracy...the plot was worked/tweaked with USN consultants to be somewhat realistic, but the flying sequences were filmed for excitement....so, I wouldn't try multiple aileron rolls as you see here...they're fun to watch...but pointless in combat...

Note too that this movie was made long before CGI became any good. These sequences were carefully briefed and flown by the guys from TOP GUN with real cameras bolted on to real airplanes like the F-14.

To this day, it's some of the best flying footage ever filmed...in fact, if you edit out all the acting, you're left with a really great 27 minute Tomcat video...

Some of the stuff in the cockpit was also silly...when Tom Cruise "goes around" to go get his wingman, he slams the throttles back through the AB gate ( the click-click that you hear) to idle and pulls back on the stick...in a Tomcat that would ensure that you slam into the deck harder and lower than intended...it sure wouldn't get you back in the air...but hey, it's HOLLYWOOD..

 

[Astro14]

Originally Posted By: GearheadTool
... this one?

That's a real missile shot by the way...with a model of an F-5 (the fearsome "MiG-28" of the movie) blowing up...again, CGI and special effects simply weren't sophisticated enough to capture what happens in a fighter...

This scene cracks me up...the maneuvering is well...slow...and more like a beginner formation flight...rather than the high-G of a real fight...but they wanted the airplanes close enough to film and get them all in the shot. so slow it was...

And the "hit the brakes" thing again...please...

 

[shell_user]

Slightly off topic ASTRO14, but what carrier was the TOP GUN movie filmed on or around? I was thinking USS ENTERPRISE(CVN-65)

 

[Astro14]

Big "E" appeared in the movie. Most of the filming was done off the coast of California, or in the ranges in Fallon, NV. The crews were based out of Miramar NAS (where Top Gun was located at the time).

I have heard that the Vinson, CVN-70, was used for flight deck scenes...but the interior shots looked like another carrier...an older one...

Here's an interesting story about the movie, you won't hear this anywhere else...I had a chance, in the mid 90's, to talk with John Lehman, who was SECNAV under President Reagan...here's what he told me back then...

Don Simpson and Jerry Bruckheimer (who produced TOP GUN) had approached the SECNAV about making this movie. They knew they needed full USN support to film on a carrier, with real planes, in real bases, to get the drama they were looking for in their movie about a young pilot (Maverick). To pitch their movie concept to the SECNAV, Simpson and Bruckheimer flew out to DC to discuss the movie over dinner.

They invited the SECNAV and his wife to one of the nicer restaurants in town, and when they sat down to dinner, they seated Mrs. Lehman next to the young actor that had been cast in the role of Maverick; Tom Cruise.

In the words of SECNAV, "I was done for!"

And it turned out to be one of the greatest recruiting campaigns ever for the US Navy. The words "Top Gun" have entered the English lexicon...and the movie has become iconic...

Whatever we spent on jet fuel and logistics to support the movie (and the USN was re-imbursed for the fuel cost, I think) we made back at least a thousand times over in public awareness, excitement, and in the quality of recruits over the next decade.

 

[Mr Nice]

Did any Navy recruiter fib and get some people to enlist with the promise of flying the Tomcat ? LOL.

The Tomcat was great at many the many air shows I've gone to... but the Blue Angels are simply amazing. I love watching the Super Hornet at a recent air show.

 

[Shannow]

Originally Posted By: Astro14
And it turned out to be one of the greatest recruiting campaigns ever for the US Navy. The words "Top Gun" have entered the English lexicon...and the movie has become iconic...

I can really believe that, being 18 at the time the movie came out

 

[Astro14]

Originally Posted By: LT4 Vette
Did any Navy recruiter fib and get some people to enlist with the promise of flying the Tomcat ? LOL. /forums/graemlins/smile.gif

One imagines that the truth might have been..."stretched"...just a bit. We did take sailors into commissioning programs...and some of those into flight programs...but the numbers were small...I wonder too what those young folks thought the odds would be...the flight programs were tough..,

I applied and had good grades in a science major. I started with 50 similar young men (great shape, good grades, passed the physical) in Pensacola for Aviation Officer Candidate School.
The more restrictive physical reduced us to 40. 20 made it to graduation. 12 made it through flight training. 3 got jets. 1 got Tomcats..

 

[JetStar]

I was a young engineer at GE aircraft engines when we were developing the F110-400 engine. We built the AFT (Augmentor, Fan, Temperature) control for the engine. It was a full authority fuel cooled analog unit based on the F110-100 control with hydromechanical back-up. Along with different engine scheduling, I do remember some cross engine discrete's having to do with burner light sync. logic, and thrust symetry. There were also discretes for AGI (Armament Gas Ingestion) to re-schedule the engine for ingestion of gun and missile gasses. The contol monitored Speed, Pressure, and temperature, and scheduled the engine parameters MFMV, AFMV, IGV, VSV, IGN, A8. Since this was essentially an analog computer, any change in scheduling resulted in hardware changes. Nearly at the same time we were working on a digital control for the Air Force F110-129 engine. The Navy did not seem interested at the time and did not adopt a digital control until the F414 engine came along for the Hornet.

 

[Astro14]

The F-110-400 worked really well in the jet. We talked once about the AB liner cooling flow balance and liner burn through....so I won't rehash that here...

There were several mods and control measures for this install. The first you mentioned was known as ATLS -asymmetric thrust limiting system. With a TF-30 in max AB the Vmca (min controllable airspeed) was140 knots. With the increase in power of the F-110 (23,800 in AB vs 17,000 for the TF-30) the Vmca was close to 185 kts with one in max AB and one failed, so, the airplane would would be in a region of uncontrollability between takeoff (140 or so) and acceleration through Vmca.

Turns out that it accelerated so well in AB you would overspend the landing gear doors on takeoff...the gear retraction sequence took about 12 seconds, during which the airplane would accelerate from rotation at 140 through max gear door speed of 280 knots. So AB takeoffs were among the prohibited maneuvers.

But a few intrepid young fighter guys (among them, an exceptionally talented naval aviator named "Shaggy") learned that at very low airspeed, you could select ATLS off, pull one engine back and rotate the airplane quickly in yaw to bring your nose back onto an adversary...

One other modification that was needed for the F-110 that was built into the AFT Logic was RATS - reduced arrest thrust system. The F-14 was among the heaviest jets to come aboard the boat. It stressed the arresting gear engines ( large hydraulic machines below decks that controlled the rate at which the arresting cable was let out to slow the airplane to a stop) to their limit. Pilots select full power (dry, not AB) on touchdown in case the hook skips the wires, the airplane only has 300 feet in which to get airborne again, so spooling up the engines is required in those 1-2 seconds.

The added thrust of the F-110 increased the load on the AG engines over the TF-30 equipped airplanes, which required increased wind over the deck vs. an F-14A to reduce the relative engagement speed of aircraft to AG to compensate for the increased load from engine thrust.

Increased wind wasn't always practical, older conventional carriers couldn't always get up the speed if the wind was calm, and considerations like sea room, tactical maneuvering of the ship, or propulsion system limits were often limiting.

So, the bring the AG load back down to that of an F-14A, the RATS system would limit core engine speed to 92% RPM with both weight on wheels and hook down, approximating the thrust of the TF-30 and making the engineering of an arrested landing the same for all models of Tomcat.

As far as the Navy's interest in the -429 FADEC - sure, we were very interested...in fact, it was part of the Tomcat 21 design at Grumman...but remember the times, the Navy's budget was being cut in the early 90s, the F-14 production line was being shut down, with the last airplanes delivered in 1992...so, we couldn't afford any upgrades to engines that worked well...what $$ we had to spend on the F-14 program was spent on delivering LANTIRN, bomb racks and other improvements to the Tomcat's operational capability.

 

[JetStar]

I had forgotten about the RATS function, IIRC we called it "Hook Stretcher".

 

[tom slick]

I worked on some of the first F110-100 flight test engines with the FADEC upgrade in the 90's.

It's interesting to read about the various parameters that were designed into the F110-400 to account for the nuances of the airframe.

For those that are interested, here are some pictures of the F110-100 which is very similar to the F110-400 that powered the F-14.

http://enginehistory.org/Museums/GEF110/f110ge100.shtml

 

[SEMI_287]

How were her flight characteristics? Heavy or light?? Whats the Vne on that bad boy?? Also you should really check out the Extra 300, Astro. Aerobatics are so much fun! Throw a few combat maneuvers in there, even better. BUT, if you want to do fun stuff make sure you wear a chute. 91.307. FARs. Fun.

 

[JetStar]

Originally Posted By: tom slick
I worked on some of the first F110-100 flight test engines with the FADEC upgrade in the 90's.

It's interesting to read about the various parameters that were designed into the F110-400 to account for the nuances of the airframe.

For those that are interested, here are some pictures of the F110-100 which is very similar to the F110-400 that powered the F-14.

http://enginehistory.org/Museums/GEF110/f110ge100.shtml

Tom were these -100 analog to digital upgrade engines (kits comprising of the fadec and cables, etc...) or were these -129's? We did both.

The F16 app used a discrete input to tell the control if it was a large duct or small duct airframe. There was a -100A analog we built for the Israelis that had an external switch mounted to the chassis that would re-schedule the engine for performance vs. longevity. The -400 engine had a much longer burner can than the -100 or -129.

I always found the roll control scheme of the F-14 interesting. No ailerons from what I have read, spoilers and elevons. Spoilers faded out as the wing sweep increases.

 

[tom slick]

These were the upgraded -100. If memory serves me correctly they added "A" and "B" to pri and sec mode and it had logic to make different decisions on faults on the ground or in the air.
I also worked on a few -129 and F101-102. We did a lot of TCTOs on those engines.
This was all at the engine shop at Edwards AFB.

I think I still have the GE information that the rep would use to inform the mechanics of upcoming changes.

 

[Astro14]

I don't think that folks appreciate how much engineering goes into each part of a sophisticated machine like a fighter aircraft...look at the complexity, the detail (and changes and upgrades) in the engines alone...

I have to run, but will answer the flight characteristics question this afternoon...it's a complex answer (of course) since the airplane was able to fly over such a broad range of speeds and had such variable aerodynamics...

Cheers,
Astro

 

[tom slick]

All it takes is installing a bolt backward or leaving a piece of FOD somewhere and people lose their life.
GE changed the design of the VSV assembly at least twice to attempt to prevent them from being mistakenly installed backward. A single backward VSV wouldn't cause a detectable performance difference but the disturbance in airflow would cause major core damage a couple of thousand hours later.

Back on topic:

Did you ever use the egress system? (of any plane)

During a carrier landing, why do try to catch the last cable?

 

[INDYMAC]

Here is a good video of a Tomcat CV landing profile.



There are 4 wires (if all are online). The 3 wire is the target zone. The OLS "meatball" provides glideslope info to the pilot. The PLAT video shows corrections being made to glideslope and centerline by the pilot. The LSO helps the pilot too, but you can't hear his audio in this PLAT tape. Centerline is important too, since too far off center can break the wire. A broken wire is catastrophic for the aircraft, as well as personnel and equipment on the flight deck. There is also a barricade that can be rigged in a couple of minutes, if the pilot requires it for landing due to an emergency. It's like a big hammock.